The present invention relates to hydraulic devices comprising a piston sliding in a bore and capable of assuming at least one stable position, as long as the force exerted on the piston is below a specific threshold, and of these, more particularly a bleed valve especially for a hydraulic brake circuit of a motor vehicle.
These hydraulic devices of stable piston position generally have a prestressed spring bearing in the piston counter to the force exerted on it. As soon as this force exceeds the threshold determined by the prestress, the differential of the pressures generated by the two opposite forces tends to move the piston in proportion to this differential. In some uses, like that described below, it is necessary to obtain an all-or-nothing mode of operation. The subject of the present invention is, therefore, such a device which is reliable and inexpensive.